1. Field of the Invention
The invention relates to cylinder locks designed to prohibit wrongful unlocking.
2. Related Art
A cylinder lock arranged on a door of an automobile is designed as follows. A plurality of tumblers are arranged so as to be movable in radial directions in a key rotor that is rotatably arranged in a rotor case, and such plurality of tumblers are urged by springs in a single direction. As the rotation of the key rotor is blocked with end portions of the tumblers engaged with tumbler engagement grooves arranged in inner circumferential portions while inserted thereinto, the cylinder lock can be locked.
To unlock the cylinder lock, a regular key is inserted into a keyhole of the key rotor. As a result, the respective tumblers are moved so as to be released from the tumbler engagement grooves by the key. As the key is rotated, the key rotor is rotated, which causes the lock lever to rotate and hence unlocks the cylinder lock.
In the cylinder lock of this type when a key other than the regular key, a screwdriver, or the like is inserted into the keyhole of the key rotor to forcibly rotate the key rotor, the end portions of the tumblers are forcibly biased onto the tumbler engagement grooves of the rotor case, which in turn breaks either the tumblers or the rotor case. As a result, the cylinder lock is no longer used again.
By the way, it is conceivable to improve the strength of the respective components of the cylinder lock. However, this requires that the thicknesses of the components be increased, which in turn imposes the problem of increasing the size of the cylinder lock as a whole.